Branch has updated to the new AdServices API. The new Apple Ads framework requires Branch iOS SDK v1.39.0.
As of February 1st, 2022 the Campaign Management API is deprecated which is used to pull cost, click, and impression data, and not the iAD framework used for attribution. If you are on this legacy iAd framework, you just need to authenticate your Apple Ads account in the Branch Dashboard to get clicks, cost and impression data reporting.